This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background and Rational: Dementia is an important central nervous system complication of HIV-1 infection. Presence of the apolipoprotein e4 (Apo e4) allele may increase risk for dementia in older HIV seropositive individuals by directly exacerbating the underlying pathophysiology of HIV induced neurodegeneration, as well as increasing risk for development of co-morbid Alzheimer's disease (AD). Objective: We propose to use a pre-existing and neurologically well-characterized HIV cohort, the Hawaii Aging with HIV cohort, to assess the effect of Apo e4 status on cortical metabolism in 52 older (age 50) HIV seropositive individuals, 26 with and 26 without the Apo e4 allele. Methods: Participants will undergo brain PET imaging, neuropsychological testing, neurological examination, and lumbar puncture. Statistical parametric mapping will be employed to determine group differences in brain metabolism associated with Apo e4 allele presence. Specific attention will be given to the frontal lobes and basal ganglia which are typically affected in HIV infection, and the temporoparietal and posterior cingulate regions which are characteristically affected in AD. Further support for co-morbid AD will be obtained by determining cerebrospinal fluid beta-amyloid and tau protein levels. As an additional aim, we will attempt to correlate neuropsychological test performance with regional cortical metabolism in HIV seropositive individuals. Proposed Involvement of CRC: Assistance from the CRC is necessary to provide financial support for costs associated with PET brain imaging, travel expenses, and for Dr. McMurtray's and Research Associate Mr. Taylor's time to conduct the proposed research project.